The track context menu should be accessible from anywhere in the track, not just on the track name

[fqueze]

Even though I know the context menu letting me show or hide a track from the same process is only available when I context-click on the track name, I keep doing context-click on the track itself, and see the normal Firefox context menu (except on the network track where I get no menu at all) instead of the profiler one.

I think when context-clicking on a track and not over a marker, we should show the track context menu.